Re: [PATCH v3] userfaultfd: reset err to be 0 when move_pages_ptes succeeded

[Foxie Flakey <foxieflakey@gmail.com>]

On Tue, 18 Aug 2026, Andrew Morton wrote:

> On Wed, 19 Aug 2026 10:08:24 +0700 (WIB) Foxie Flakey <foxieflakey@gmail.com> wrote:
>
> >
> > During move_pages() operation, when move_pages_ptes() returns EAGAIN,
> > the error code is not cleared even after we processed it. This leads
> > to a successful retry but then the same pages are retried again due to
> > the stale error code. This time move fails because pages are already
> > moved, loop is terminated and move_pages() reports a failure.
> > Clear the error code once we processes EAGAIN.
> >
> > Fixes: 50944692052b ("userfaultfd: opportunistic TLB-flush batching for present pages in MOVE")
> > Assisted-by: ChatGPT:GPT-5.6-Luna
> > Signed-off-by: Bryan Lim <foxieflakey@gmail.com>
>
> Thanks, Bryan.

No, problem. Thank you for your time. If you don't mind this, I would
prefer keep to be called as Foxie unless its required to be Bryan Lim like
the sign off. Sorry, if it took a while for me to understand.

> More paperwork: the signoff is supposed to match the Author:.  The way
> to do this is to add an explicit From: line at start-of-changelog.  If
> this is not present, we fall back to the email envelope's From:.

Noted. I'll keep that in mind for my future patches.

> > --- a/mm/userfaultfd.c
> > +++ b/mm/userfaultfd.c
> > @@ -2085,8 +2085,10 @@ static ssize_t move_pages(struct userfaultfd_ctx *ctx, unsigned long dst_start,
> >  		}
> >
> >  		if (err) {
> > -			if (err == -EAGAIN)
> > +			if (err == -EAGAIN) {
> > +				err = 0;
> >  				continue;
> > +			}
> >  			break;
> >  		}
>
> I'll queue it, with an adjusted From:, as above.

Thank you!

> Could reviewers please advise on whether we should backport this into
> -stable kernels?
>
>